Field of the Invention
The present invention relates to a toner used in image-forming methods such as electrophotographic methods, electrostatic recording methods, and toner jet methods.
Description of the Related Art
The demands on printers and so forth for size reduction and greater energy savings have been increasing in recent years. One approach to size reduction is to improve the tinting strength of the toner. Improving the tinting strength of a toner makes it possible to carry out image formation using less toner, and as a result the size of the toner container can be reduced.
Investigations have been carried out into enhancing the pigment dispersibility in order to improve the tinting strength of toner. Pigment dispersants having a segment adsorbed to the pigment and a polymer segment that exhibits a good intimacy with the dispersion medium for the pigment are in use as a means for enhancing the dispersibility of the pigment in a toner. WO 99/42532 describes an example that uses Solsperse (registered trademark) (The Lubrizol Corporation) as a comb-shaped polymeric dispersant that has an acidic or basic moiety. Japanese Patent Application Laid-open No. 2010-152208 describes an example that uses, as a polymeric pigment dispersant for toners, a dispersant in which an azo or bisazo chromophore having an acetoacetanilide substituent is bonded to a polymer. These realize toners that have high tinting strengths.
On the other hand, fixing at lower temperatures is a property required of a toner in order to achieve greater energy savings. Investigations have therefore been carried out into the use of crystalline polyester. Crystalline polyester has the property (sharp melt property) of undergoing almost no change in viscosity up to its melting point and then immediately softening all at once when its melting point is exceeded. The introduction of a crystalline material into a toner can bring about softening of the toner by the heat applied during fixing without causing the heat-resistant storability to deteriorate, and for this reason can be expected to enhance the fixing performance (low-temperature fixability) at low set temperatures. A toner that uses a crystalline polyester is proposed in Japanese Patent Application Laid-open No. 2014-167602, and this toner makes it possible for the low-temperature fixability to co-exist in good balance with the heat-resistant storability.